The present invention relates to the processes of how to fabricate the microchannel plate for use in the image intensifier, UV ray detector, ion detector or charge particle detector.
The assignee of the present invention already filed a patent application in Japan, which was published as Japanese Patent Publication No. 25934/1982, entitled "Process of how to fabricate the microchannel plate". The summary of this published application is given as follows:
A glass core, which can be dissolved by acid, is covered with a glass cladding, which cannot be dissolved by acid, so as to make a single glass fiber. A plurality of the glass fibers are arranged in parallel and bound to form a bundle of glass fibers. These fibers are heated until the surfaces of these fibers are sintered to form a single bound structure.
After the process abovementioned, the glass fiber bundle can be sliced along the direction perpendicular to its optical axis so as to make a plate. The glass core can then be solved by acids, to form a bundle of pipes.
The glass clad, which cannot be dissolved by acid, contains 35 to 50 weight percents of silicon di-oxide (SiO.sub.2); two to ten weight percents of one or more of sodium oxide (Na.sub.2 O), potassium oxide (K.sub.2 O) and lithium oxide (Li.sub.2 O); 30 to 55 weight percents of lead oxide (PbO) and 0.5 to 7.0 weight percents of one or more of titanium di-oxide (TiO.sub.2) and zirconium di-oxide (ZrO.sub.2).
The inner surfaces of the microchannel plate are activated by the other process and then a pair of electrodes are formed at both sides of the plate. This activated state is called the initial state. The initial microchannel plate is heated within a vacuum to exhaust gases therefrom during baking process.
The microchannel plate fabricated, activated and baked in accordance with the procedures mentioned above has a gain much lower than the value which can be obtained before the baking process. If we define the total output charge as an integral of the output current till the end of life, the microchannel plate has a total output charge of 1.times.10.sup.-1 coulomb/cm.sup.2, if the end of life is defined the time point when the gain becomes 50% of the gain immediately after the baking process.
FIG. 4 shows the gains of the microchannel plate in the respective steps of the fabrication processes in the above referred-to Japanese publication. The gain obtained after the baking process is 20 to 30% of the initial state microchannel plate.
Scrubbing process is that of actually operating the microchannel plate, after the baking process, and to strike electrons to the inner surface of the microchannel plate. After the scrubbing process, the gain of the microchannel plate decreases a little. The X-axis of the graph in FIG. 4 indicates the voltage across the micro-channel plate electrodes.
The objective of the invention is to present the processes of how to suppress the decrease of the gain after the microchannel plate is baked within a vacuum and how to elongate the life of the microchannel plate.